This contract allows the National Institute on Aging to work cooperatively with the National Center for Health Statistics in conducting analyses of appropriate data sets as the need for such analyses arises. By working in this joint manner pertinent questions can be answered more efficiently and the level of research is likely to be of higher quality than if either institute worked alone. At the present time the research topics include: 1) the relationships between the existence of fluoride in drinking water and osteoporosis, 2) changes in incidence of stroke, 3) analysis of Family Data, 4) differences in lean body mass between the sexes and 5) mortality rates from accidents.